On my 83 suburban 4x4 with a 350, I’m having light/medium throttle back firing issues, I’ve tried everything. Timing is at 12 degrees initial, 38 total I’ve got 18 inches of vacuum at idle float bowls are set right as best as I can tell, it’s a Holley 4160, I can’t figure this out it’s driving me nuts. What y’alls opinion??

I will on Friday when I can get new gaskets, the previous owner of this truck rtv’d the hell outta the gasket, but I put a buddies Edelbrock carb on it this morning, and so far no popping or backfires at all. It may have a bad cam the last owner wasn’t very kind to this truck at all

I assume it's only popping back through the carb when it happens? I had something similar happen mainly out the exhaust pipe, checked cam and rockers, timing etc. Turned out to be fouled plugs. Sometimes it's the little things.